<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>html5进度条</title>

    <style type="text/css">
        * {
            margin: 0;
            padding: 0;
            list-style-type: none;
        }

        a, img {
            border: 0;
        }

        body {
            background: #111;
        }

        canvas {
            background: #111;
            border: 1px solid #171717;
            display: block;
            left: 50%;
            margin: -51px 0 0 -201px;
            position: absolute;
            top: 50%;
        }
    </style>

</head>

<body>

<script>
    /*========================================================*/
    /* Light Loader
    /*========================================================*/
    var lightLoader = function(c, cw, ch){

        var _this = this;
        this.c = c;
        this.ctx = c.getContext('2d');
        this.cw = cw;
        this.ch = ch;

        this.loaded = 0;
        this.loaderSpeed = .6;
        this.loaderHeight = 10;
        this.loaderWidth = 310;
        this.loader = {
            x: (this.cw/2) - (this.loaderWidth/2),
            y: (this.ch/2) - (this.loaderHeight/2)
        };
        this.particles = [];
        this.particleLift = 180;
        this.hueStart = 0
        this.hueEnd = 120;
        this.hue = 0;
        this.gravity = .15;
        this.particleRate = 4;

        /*========================================================*/
        /* Initialize
        /*========================================================*/
        this.init = function(){
            this.loop();
        };

        /*========================================================*/
        /* Utility Functions
        /*========================================================*/
        this.rand = function(rMi, rMa){return ~~((Math.random()*(rMa-rMi+1))+rMi);};
        this.hitTest = function(x1, y1, w1, h1, x2, y2, w2, h2){return !(x1 + w1 < x2 || x2 + w2 < x1 || y1 + h1 < y2 || y2 + h2 < y1);};

        /*========================================================*/
        /* Update Loader
        /*========================================================*/
        this.updateLoader = function(){
            if(this.loaded < 100){
                this.loaded += this.loaderSpeed;
            } else {
                this.loaded = 0;
            }
        };

        /*========================================================*/
        /* Render Loader
        /*========================================================*/
        this.renderLoader = function(){
            this.ctx.fillStyle = '#000';
            this.ctx.fillRect(this.loader.x, this.loader.y, this.loaderWidth, this.loaderHeight);

            this.hue = this.hueStart + (this.loaded/100)*(this.hueEnd - this.hueStart);

            var newWidth = (this.loaded/100)*this.loaderWidth;
            this.ctx.fillStyle = 'hsla('+this.hue+', 100%, 40%, 1)';
            this.ctx.fillRect(this.loader.x, this.loader.y, newWidth, this.loaderHeight);

            this.ctx.fillStyle = '#222';
            this.ctx.fillRect(this.loader.x, this.loader.y, newWidth, this.loaderHeight/2);
        };

        /*========================================================*/
        /* Particles
        /*========================================================*/
        this.Particle = function(){
            this.x = _this.loader.x + ((_this.loaded/100)*_this.loaderWidth) - _this.rand(0, 1);
            this.y = _this.ch/2 + _this.rand(0,_this.loaderHeight)-_this.loaderHeight/2;
            this.vx = (_this.rand(0,4)-2)/100;
            this.vy = (_this.rand(0,_this.particleLift)-_this.particleLift*2)/100;
            this.width = _this.rand(1,4)/2;
            this.height = _this.rand(1,4)/2;
            this.hue = _this.hue;
        };

        this.Particle.prototype.update = function(i){
            this.vx += (_this.rand(0,6)-3)/100;
            this.vy += _this.gravity;
            this.x += this.vx;
            this.y += this.vy;

            if(this.y > _this.ch){
                _this.particles.splice(i, 1);
            }
        };

        this.Particle.prototype.render = function(){
            _this.ctx.fillStyle = 'hsla('+this.hue+', 100%, '+_this.rand(50,70)+'%, '+_this.rand(20,100)/100+')';
            _this.ctx.fillRect(this.x, this.y, this.width, this.height);
        };

        this.createParticles = function(){
            var i = this.particleRate;
            while(i--){
                this.particles.push(new this.Particle());
            };
        };

        this.updateParticles = function(){
            var i = this.particles.length;
            while(i--){
                var p = this.particles[i];
                p.update(i);
            };
        };

        this.renderParticles = function(){
            var i = this.particles.length;
            while(i--){
                var p = this.particles[i];
                p.render();
            };
        };


        /*========================================================*/
        /* Clear Canvas
        /*========================================================*/
        this.clearCanvas = function(){
            this.ctx.globalCompositeOperation = 'source-over';
            this.ctx.clearRect(0,0,this.cw,this.ch);
            this.ctx.globalCompositeOperation = 'lighter';
        };

        /*========================================================*/
        /* Animation Loop
        /*========================================================*/
        this.loop = function(){
            var loopIt = function(){
                requestAnimationFrame(loopIt, _this.c);
                _this.clearCanvas();

                _this.createParticles();

                _this.updateLoader();
                _this.updateParticles();

                _this.renderLoader();
                _this.renderParticles();

            };
            loopIt();
        };

    };

    /*========================================================*/
    /* Check Canvas Support
    /*========================================================*/
    var isCanvasSupported = function(){
        var elem = document.createElement('canvas');
        return !!(elem.getContext && elem.getContext('2d'));
    };

    /*========================================================*/
    /* Setup requestAnimationFrame
    /*========================================================*/
    var setupRAF = function(){
        var lastTime = 0;
        var vendors = ['ms', 'moz', 'webkit', 'o'];
        for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x){
            window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];
            window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame'] || window[vendors[x]+'CancelRequestAnimationFrame'];
        };

        if(!window.requestAnimationFrame){
            window.requestAnimationFrame = function(callback, element){
                var currTime = new Date().getTime();
                var timeToCall = Math.max(0, 16 - (currTime - lastTime));
                var id = window.setTimeout(function() { callback(currTime + timeToCall); }, timeToCall);
                lastTime = currTime + timeToCall;
                return id;
            };
        };

        if (!window.cancelAnimationFrame){
            window.cancelAnimationFrame = function(id){
                clearTimeout(id);
            };
        };
    };

    /*========================================================*/
    /* Define Canvas and Initialize
    /*========================================================*/
    if(isCanvasSupported){
        var c = document.createElement('canvas');
        c.width = 400;
        c.height = 100;
        var cw = c.width;
        var ch = c.height;
        document.body.appendChild(c);
        var cl = new lightLoader(c, cw, ch);

        setupRAF();
        cl.init();
    }

</script>

</body>
</html>